ML19249B392

LER 79-087/03L-0:on 790731,operators Twice Received Control Rod Sequence Fault Alarm.Caused by Faulty Integrated Circuit in Auxiliary Power Supply of Command Logic String.Circuit Replaced & Proper Operation Verified

ML19249B392
Person / Time
Site:	Davis Besse
Issue date:	08/27/1979
From:	Hitchens D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19249B386	List: ML19249B385 ML19249B392
References
LER-79-087-03L, LER-79-87-3L, NUDOCS 7909040364
Download: ML19249B392 (2)

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NRC FORM 66 U. S. NUCLEAI4 REGULATORY COMMISSION (7-77)

LICENSEE EVENT REPORT (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

CONTROL BLOCK: l 1

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EVENT DESCRIPTION AND PROB ABLE CCNSEQUENCES h o 2 l While performing a main turbine steam valve test, operators twice received a control l o 3 l rod drive sequence fault caused by Group 6 rods moving of f their out limit to 95%. [

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o 4 [ This placed the unit in Action Statement (a) of T.S. 3.1.3.6. There was no danger to j o 3 l the health and safety of the public or station personnel. Rod cotion was minimal and ;

o s l caused no noticeable reactivity or core power distribution changes. (NP-33-79-101)  ;

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o 8 l 80 7 8 9 SYSTEM CAUSE CAUSE COYP. VALVE CODE CCDE SUSCOCE COMPCNENT CODE SUBCODE SUSCOOE

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i o lrhe cause of this occurrence was a faulty integrated circuit on a logic gate module in) li j i l 1 the auxiliary power supply of the command logic string. Instrument and Control per-  ;

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i 2 isoanel replaced the integrated circuit and verified proper operation. ,

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1 4 l 7 8 9 80 F ACitiTV VETwCOOF STATUS  % POW E R CTHER STATUS CISCOV E AY DISCOVERY DESCRIPTION Al@lOperatorobservation

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TOLEDO EDISON COMPANY

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DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-101 DATE OF EVENT: July 31, 1979 FAC1Lii Y: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of Group 6 out limit Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 2680 and Load (Gross MWE) = 880 Description of Occurrence: On July 31,1979 at 0110 hours0.00127 days <br />0.0306 hours <br />1.818783e-4 weeks <br />4.1855e-5 months <br /> and at 0140 hours0.00162 days <br />0.0389 hours <br />2.314815e-4 weeks <br />5.327e-5 months <br /> while performing PT 5193.01, " Main Turbine Steam Valve Tests", operations personnel re-ceived a Control Rod Drive Sequence Fault. In both instances, they noticed that Group 6 had moved off of its out limit to approximately 95%. This placed the unic in the Action Statement (a) of Technical Specification 3.1.3.6. This Tec.hnical Speci-fication requires Group 6 to be within the insertion limits during Modes 1 and 2.

Action Statement (a) instructs the unit to restore the rod (s) to within the insertion limit within two hours.

In each case, operators t=nediately pulled Group 6 back to its out limit which re-moved the unit from the Action Statement (a) of Technical Specification 3.1.3.6.

PT 5193.01 was suspended until the problem could be resolved.

Designation of Annarent Cause of Occurrence: The cause of this occurrence is attri-buted to a faulty integrated circuit (IC 2) on a logic cate module in the auxiliary power supply of the command locic string.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The Group 6 rod motion was minimal and no noticeabla reacti-vity or core power distribution ef fects occurred.

Corrective Action: Instrument an:1 Control personnel were called in and the IC was replaced and proper operation verified under work request IC-055-014-79. FT 5193.01 was successfully completed on July 31, 1979. The unit had been removed from the Action Statement of Technical Specification 3.1.3.6 i==ediately af ter the occurrence when operations personnel pulled Group 6 back to its out limit.

Failure Data: fhere have been no previously reported similar events.

1 LER #79-087

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